docs: def close(self):
          """Close all connections in the pool."""
          self._condition.acquire()
          try:
              while self._idle_cache: # close all idle connections
                  con = self._idle_cache.pop(0)
                  try:
                      con._close()
                  except Exception:
                      pass
                  self._connections -=1
              self._condition.notifyAll()
          finally:
              self._condition.release()